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NIST (National Institute of Standards and Technology) using Vic-3D for digital image correlation (DIC)

NIST is using the Vic-3D dig­i­tal image cor­re­la­tion (DIC) sys­tem to ana­lyze stress in bridges. By using DIC, they try to under­stand the impact of stress­es and strains on the met­al con­nec­tors of bridges in order to avoid dam­age or failure.

NIST is pre-strain­ing a wide plate with dig­i­tal image cor­re­la­tion (DIC) to deter­mine the small-scale spec­i­men sec­tion­ing plan:

https://www.nist.gov/video/pre-straining-pipeline-steel-plate

NIST is con­duct­ing a CWP test with dig­i­tal image cor­re­la­tion (DIC) to deter­mine local and remote strains used to deter­mine the Ten­sile Strain Capac­i­ty of a flawed pipe girth-weld:

https://www.nist.gov/video/curved-wide-plate-testing

NIST is mak­ing an SE(T) test with dig­i­tal image cor­re­la­tion (DIC) show­ing the asym­met­ric strain gra­di­ent of a spec­i­men notched in the heat-affect­ed zone:

https://www.nist.gov/video/single-edge-notch-tension-testing

DIC measurements on structural concrete

The ETH Zürich — one of our long­stand­ing cus­tomers — pro­vides on the fol­low­ing web­site their research project. They ana­lyze the accu­ra­cy of dig­i­tal image cor­re­la­tion with­in the scope of rein­forced con­crete. Prof. Dr. Wal­ter Kauf­mann and Dr. Jaime Mata Fal­cón are mem­bers of the project.

   eth-zuerich-2

Full-field strain mea­sure­ment in rebar tension 

test: fail­ure phase.

Strain Gauge Comparison

In this exam­ple a Vic-3D mea­sure­ment with 5MP CMOS Cam­era was per­formed. The acryl spec­i­men is fixed in a ten­sile test­ing machine. A strain gauge is attached at the back in com­bi­na­tion with a SCAD 500 strain gauge ampli­fi­er. The out­put of the SCAD 500 was con­nect­ed to the DAQ of the DIC sys­tem. The strain results are record­ed par­al­lel with the Vic-3D mea­sure­ment and plot­ted in a dia­gram. The cam­era type is equipped with Sony 5Mpx Pregius sen­sor, 75 fps.

Strain Gauge Comparison-1  Strain Gauge Comparison-1a

Image 1: Vic-3D mea­sure­ment of the acryl specimen

 

Strain Gauge Comparison-2

 

 

 

 

 

 

 

 

Image 2: Com­par­i­son of strain gauge data (red curve) and DIC Strain data (black curve)

 

The Vic-3D data match near­ly per­fect with the strain gauge data. Even at low strains the dif­fer­ence is less than 25 micro strain.

NDT of Carbon-NOMEX (honeycomb core) composite: Dynamic loading on a large yacht hull

Marine NDE (Spain) used the tech­ni­cal advan­tages of our Shearog­ra­phy-Sys­tem espe­cial­ly in com­bi­na­tion with the dynam­ic exci­ta­tion for non-destruc­tive exam­i­na­tion (NDE) of large areas such as com­plete yacht hulls (see image below). The hull with a lenghts of 30,5m was a car­bon-fir­ber-com­pos­ite and part of high per­for­mance sail­ing yacht in build. Because of the full-field method (100% of the inspect­ed area is exam­ined), the test­ing of the entire hull required only 240 shots, in three workdays.

 

The yacht hull con­sists of a sand­wich con­struc­tion, where are in par­tic­u­lar used hon­ey­comb cores (NOMEX).

Marine NDT1Marine NDT2

 

 

 

 

 

 

On the left — A shearo­gram of a detect­ed bond­ing defect (in red oval). The yel­low X marks the loca­tion of the core sam­ple shown at the right. The destruc­tive test con­firms the shearo­gram’s indi­ca­tion that there is a sig­nif­i­cant nev­er-bond between the hon­ey­comb core mate­r­i­al and the film adhe­sive in this area.

 

Deformation Measurement

The fol­low­ing video clips show a defor­ma­tion- or strain-mea­sure­ment of a met­al spring ele­ment, mea­sured by using Vic-3D.

The first defor­ma­tion mea­sure­ment would be made in the X direction.

 

The sec­ond defor­ma­tion mea­sure­ment would be made in the Y direction.

 

The third defor­ma­tion mea­sure­ment would be made in the Z direction.

 

In the last case you see the result of the strain measurement.

Motion Measurement on Rear Swinging Fork

The video shows the appli­ca­tion of a stereo image cor­re­la­tion (phase syn­chro­nized) for a three-dimen­sion­al dis­place­ment mea­sure­ment or move­ment analy­sis (Vic-3D).

The used stereo cam­era sys­tem is based on two 5 Mpix­el cam­eras with a frame rate of 6Hz (at full res­o­lu­tion) in com­bi­na­tion with the isi-sys syn­chro­niza­tion and trig­ger device for stro­bo­scop­ic obser­va­tion of peri­od­ic events.

X

Four mea­sure­ment areas (hydraulic cylin­der — below, wheel hub — left, swingarm — mid­dle and lin­ear unit — right above) with speck­le pat­terns were mon­i­tored for the eval­u­a­tion. The vec­tor arrows rep­re­sent the cur­rent dis­place­ment state.

 

Combination Stereomicroscope and Vic-3D digital image correlation

Appli­ca­tion exam­ples of a spe­cial stere­omi­cro­scope in com­bi­na­tion with Vic-3D dig­i­tal image cor­re­la­tion on elec­tron­ic components.

Stereomikroskop

Image 1: Mea­sure­ment setup

Mea­sure­ment set up: Stereo micro­scope mount­ed on x‑y-z-microtable (back­side) and ten­sile machine (right).

Stereomikroskop2

Image 2: Strain in x‑direction

Stereomikroskop3

Image 3: Strain in y‑direction

Strain dis­tri­b­u­tion of a half cut capac­i­tor-chip (left part) and its sol­der­ing area (round sec­tion). The board is under
bend­ing load. The board is ver­ti­cal on the right sight of the image. The local red area is show­ing a crack in the
sol­der­ing part. Image area approx. <2mm.

 

Lötkugel

Image 4: The main strain of mea­sur­ing a sol­der ball d=300µm under hor­i­zon­tal shear stress is shown.